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6 September 2011 Leaf-litter decomposition in headwater streams: a comparison of the process among four climatic regions
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The main purpose of our work was to elucidate factors responsible for the geographical differences in leaf-litter decomposition rates in Spanish oligotrophic headwater streams. Decomposition experiments with alder (Alnus glutinosa) leaf litter were carried out in 22 headwater streams in 4 different climatic regions across the Iberian Peninsula (Cornisa Cantábrica, Cordillera Litoral Catalana, Sierra de Guadarrama, and Sierra Nevada). Streams that were similar in size, flowed mainly over siliceous substrate in catchments with scarce human settlements and activities, and fell within a range of low nutrient concentrations were chosen in each region. Breakdown rates were regionally variable and were low (0.109–0.198% ash-free dry mass [AFDM]/degree day [dd]) in the Cornisa Cantábrica, the most mesic and Atlantic region, and high (0.302–0.639% AFDM/dd) in Sierra de Guadarrama, one of the coldest and most inland areas. Temperature was not the determining factor affecting differences in breakdown rates among regions, and breakdown rates were not related to concentrations of dissolved nutrients. However, microbial reproductive activity (sporulation rates) was significantly correlated with dissolved P concentration. Breakdown rates were explained better by presence and feeding activities of detritivores than by decomposer activity. Incorporation of breakdown rates in assessment schemes of stream ecological status will be difficult because leaf processing does not respond unequivocally to environmental factors when climatic regions are considered. Thus, regional adjustments of baseline standards in reference conditions will be required.

The North American Benthological Society
Jesús Pozo, Jesús Casas, Margarita Menéndez, Salvador Mollá, Inmaculada Arostegui, Ana Basaguren, Carmen Casado, Enrique Descals, Javier García-Avilés, José M. González, Aitor Larrañaga, Enrique López, Mirian Lusi, Oscar Moya, Javier Pérez, Tecla Riera, Neftalí Roblas, and M. Jacoba Salinas "Leaf-litter decomposition in headwater streams: a comparison of the process among four climatic regions," Journal of the North American Benthological Society 30(4), 935-950, (6 September 2011).
Received: 17 November 2010; Accepted: 1 June 2011; Published: 6 September 2011

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